1. Field of the Invention
The present invention relates to an inkjet printing machine that discharges an ink from an inkjet head to perform printing.
2. Description of the Related Art
An inkjet printing machine that discharges an ink drop on a printing medium from a nozzle while moving the inkjet head including a plurality of the nozzles is known in the art (See, for example, Japanese Patent Application Laid-Open No. 2005-262581).
Such an inkjet printing machine is sometimes used to perform printing on a printing medium having an uneven surface. If the height of the inkjet head from the printing medium having the uneven surface is kept constant, a distance (a head gap) between the inkjet head and the surface of the printing medium varies depending on the position of the inkjet head with respect to the printing medium. Such a variation in the head gap causes a landing misalignment of the ink drop. Therefore, if printing is performed by discharging an ink from a constant-height inkjet head on a printing medium having an uneven surface, there is a possibility of occurrence of degradation in the printing quality due to a landing misalignment of the ink drop.
If the height of the inkjet head can be adjusted depending on the uneveness of the surface of the printing medium, the variation in the head gap can be reduced. Accordingly, degradation in the printing quality due to the landing misalignment of the ink drop can be reduced.
However, even if the height of the inkjet head is adjusted, the head gap may be different for each of the nozzles depending on the state of the unevenness of the surface of the printing medium. Therefore, the head gap can go out of an appropriate range thereof for some of the nozzles, which causes occurrence of the landing misalignment of the discharged ink drop. As a result, the printing quality may degrade.